Optional connect option to indicate to an MQTT server that all previous connection data
for this client should be removed and that subscriptions should be deleted when the client
disconnects explicitly or unexpectedly.

Option name used on send requests to specify the target client mode.
This can either be default to 'jms' or 'mq'. The default is 'jms' which
means an RFH2 header is sent with the message whereas the 'mq' setting
means no RFH2 is included.